The mother of the man identified as "Jihadi John" recognized immediately from his voice that her son was the alleged killer when he appeared in his first beheading video in August, Kuwaiti government officials told ABC News.

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The father of Mohammed Emwazi, who was questioned recently in Kuwait, told authorities the family last heard from his son in mid-2013 when the younger Emwazi called them from Turkey. Emwazi said he was going to do humanitarian work in Syria, the father said, according to the officials. Emwazi's father, a former policeman, said he's been waiting for news of his son's death ever since.

Instead of doing humanitarian work, Emwazi allegedly linked up with ISIS and has appeared in videos online apparently beheading Westerners, including several who were actual humanitarians. Late Tuesday, a British newspaper reported Emwazi's father had denied the Kuwaiti officials' claims that his wife recognized their son's voice in the videos.

The FBI said in September it had identified the black clad figure known in the media as "Jihadi John", but the identity was kept secret until it was reported last week.

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An image of Mohammed Emwazi his time at the University of Westminster, published in the British press Feb. 27, 2015.

Ever since, a complex picture is emerging of the alleged murderer's life before ISIS. Born in Kuwait, Emwazi moved with his family to London when he was a boy.

A school picture captured what appeared to be an angelic smile, but a teacher told the BBC Emwazi had anger management issues, for which he eventually went to therapy.

A former boss of Emwazi's in Kuwait, when Emwazi briefly lived there in 2010, told The Guardian that Emwazi was a stellar employee, "calm and decent."

"He was the best employee we ever had," the former boss said of the then 21-year-old.

Even later, a member of the British activist group CAGE told reporters he saw Emwazi as a "beautiful young man."

But at the same time, Emwazi was linked by court documents to a number of alleged jihadists in London who purportedly supported a terror group in Somalia.

In recent years Emwazi had attempted to move back to Kuwait to pursue a computer science job there but was denied entry, according to an official with CAGE, with whom he corresponded. Instead, Emwazi is alleged to have eventually gone to join ISIS.

Now, a former ISIS fighter says Emwazi is being used by the terror group.

"ISIS play him like a piano, a celebrity to attract our Muslim brothers in Europe," the fighter told the BBC. "But some think he is showing off, they think he is being used by ISIS."

The fighter described Emwazi as cold and "strange" when the two met in Syria.

Still, Emwazi is a high-value target for American and coalition airstrikes. But authorities told ABC News he has been careful to avoid using computers or his cell phone, which could give away his location.

[Editor's Note: This report has been updated to reflect that officials were referencing Emwazi's father's statements to them. It is unclear if his mother was interviewed as well.